A process for the preparation of zirconia is known from French Patent No. 2,590,887 teaching the use of an additive to obtain a relatively high surface area zirconia, that still has a relatively high surface area after sintering, i.e., in the state wherein it is to be used as a catalyst or catalyst support. The additives used to this purpose are the oxides of silicon, rare earth metals and aluminum. The additives are used in an amount of about 1 to 10%, preferably 2 to 5%. A simple mixing process resulting into an intimate mixture of the zirconia and the oxides suffices. A coprecipitation of a zirconium oxide precursor with the precursors of the further elements mentioned, is also suitable. The preferred method is the impregnation of zirconium oxide with a solution of at least one salt precursor of the further oxides. The highest specific surface area reached (m.sup.2 /g) is 90 of a treatment at 400.degree. C. Treatments at a higher temperature result into lower specific surface areas. One of the examples is a comparison and uses no additives. The specific surface area reached is 80 m.sup.2 /g after a heat treatment at 400.degree. C. and 20 m.sup.2 /g after a heat treatment at 900.degree. C. (The treatment takes 6 hours).
U.S. Pat. No. 4,440,875 teaches a process for the production of hydrocarbons from synthesis gas wherein a catalyst consisting of zirconium oxide promoted with at least one alkali metal compound is used. Preferably the zirconium oxide has a specific surface area in the range from 20 to 500 m.sup.2 /g and is the alkali metal compound a potassium compound. The only example, however, describes just a specific surface area of 122 m.sup.2 /g resulting from a previous calcination step carried out in air for 2 hours at 450.degree. C. The catalyst is obtained by dissolving zirconium oxychloride in water and gradually adding ammonia to the solution until the pH value of the solution is in the range from 7 to 10. The precipitated zirconium hydroxide is separated from the solution by filtration and washed. The filtration residue is subsequently calcined from 1 to 24 hours in the air at a temperature in the range of from 300.degree. C. to 1000.degree. C.
The addition of an alkali metal compound to the catalyst improves the selectivity for butene.
The Journal of Physic. Chem. Institute 24-06-85 of the Soviet Union teaches the production of zirconium dioxide with a high specific surface area by treating a solution of zirconium nitrate with ammonia and washing the obtained gel, separating and drying it. It is then heated for 2 to 10 hours at 150.degree. C. to 175.degree. C. under a steam pressure of 6 to 10 atm. The specific surface area is 105 m.sup.2 /g.
U.S. Pat. No. 4,822,575 teaches a process for the preparation of zirconium compositions which on calcination form zirconia. The zirconium compositions are prepared by the addition of an ammonia source to an aqueous zirconium sulfate solution to give a solution pH in the value of from 0.1 to 2.5.
A general conclusion from the several disclosures is that up to now it was very difficult to reach a higher specific surface area after sintering of greater than 100 m.sup.2 /g. In general the surface area was 80 to 100 m.sup.2 /g.
Now a process has been found that yields a convenient method for a zirconia having a surface area of more than 125 m.sup.2 /g after calcination, preferably more than 150 m.sup.2 /g after calcination, more preferably more than 200 m.sup.2 /g after calcination.